Electrical control circuits for thermionic rectifiers



April 9, 1935. D. E. ODONOVAN 1,997,011

ELECTRICAL CONTROL CIRCUITS FOR THERMIONIC RECTIFIERS Filed NOV. 10, 1952 INVENTOR DANIEL E O'DONOVAN Patented Apr. 9, 1935' PAT E 1,997,011 ELECTRICAL CONTROL CIRCUITS ron 7 THERMION'IC RECTIFIERS Daniel Edward ODonovan, Chelm sford, England,

assignor to Radio Corporation" corporation of Delaware of 'Americag a Application November 10, 1932, Serial No. 641,954 I e 1 In Great Britain November 20, 1931 p 1 12 Claims.

improved automatic control circuit of simpleand economical construction and adapted to occupy comparatively small space, for performing the protective function in question.- 1

Jlccording to this invention, a control circuit for protecting a thermionic rectifier or like device in the manner described comprises acomparaw tively slow'acting thermostatic relay, a contact closed byv said relay when said relay is cold and adapted to complete the circuit of a quick acting relay, a contact closed upon energization of the said quick acting relay and connected in parallel with said first mentioned contact, a further contactadapted .to be closed upon energization of the quick acting relay and connected tocomplete aheating circuit for the thermostatic relay and,

two further contacts in series with one another in an anode potential supply lead for the thermionic rectifier or the like, one of said last men: tioned' contacts being adapted to be closed by the quick acting relay when energized and the other being adapted to. be closed by the then- 355 mostaticrelay when 'hot.

The mvent'on 18 illustrated in the accompany-- ing drawing which shows one way of carrying out the-invention as applied to a full wave mercury vapourhot cathode rectifier.

M, "Referring to the drawing potential is supplied to the anodes, l, 2 of the rectifier3 through a transformer 4 having a centretappe'd secondary in the usualway, the primary of said transformer being connectedacross the mains-.M or other energy} supply through armanually. operablemain switch 5 and through two contacts T1 R1 in series. The

contact T1 is adapted'to'be closed by a thermo static relay Tconsisting of a bimetallic strip, the

said contact being closed whenlthe relay is hot. The other contact R1 is adaptedfto be closed by a quick acting relay R- whose winding is energized from'jth'e supply through a second contact T2 of the thermostatic -relay, and adapted to be closed when said relay is closed. There is also provided a maintaining contact R2 in'parallelwith the contact T2 said maintaining contact be:

ing adapted to be closed by thequickacting relay R when energized. The circuitfor the wind-- ing of the'quick acting relay is completed through the primary 6 of a transformer having two secondaries, one secondary I being centretapped andserving as in the usual way for heating the filaments 8 of the rectifier, and the other secondary- Sserving to supply heating current for the ther-v mostatic relay, the heatingcircuit extending from the secondary through the bimetallic strip,

through a further contact R3, adapted to beclosed when the quick acting relay is closed, andthence back to the heating secondary 79.

, It will be seen that with this arrangement,

assuming thebimetallic stripfto'becold, when the masterj switch 5 isclosed a circuit will 'be made through the winding of the quick acting relay R via the primary 6 and through the contact T The quick acting relay will, therefore, be energized and will close all its contacts, the contact Rs completing thefheating circuit for the\ bimetallic strip, the contactRz maintaining the circuitfor ithelwihding of the quick acting relay, and the contacteRi being in. the anode supply lead to theprimary of the trans former 4. The bimetallic ,strip will therefore be heatedandwill bend, opening thecontact'lz through which-the quick acting relay circuit was originally made and closing the contact T1 in the anode supply circuit. Power will therefore be applied the rectifier. If now the high tension supply fails orif the mainfswitch is' opened thequick acting relay will be deenere, gized and cannot be reenerg'ized until the bimetallic strip has cooled down sufiiciently to reach it's c Id position, and close the contact T2 in parallel withthe maintaining'contact'Rz for the quick acting relay. 7 V I Itwillbe seen therefore thatthe arrangement provides the following features of inherent pro tection automatically: I

(1) The anode supply transformer cannot'tbe energized until a certain time delay has elapsed after switching on the filament, this time delay being of course determined in accordance with theprotective requirements of the rectifier to beprotected, and, V 1

(2) The high tension supply transformer is. disconnected substantially instantly if I the power supply is interrupted, and if this occurs the supply to the anode energizing transformer cannot be reconnected until the-thermostatic relay has cooled andbeen heated again. D

Having now particularly described and: ascer-.

said series contacts being closed by said slow acting thermostatic relay when hot. i

9. A control circuit for thermionic apparatus, means for protecting said apparatus until a predetermined cathode temperature is attained, said means comprising an anode supply circuit, a slow acting relay for closing, a switch connected in series with the anode supply circuit, a quick acting relay for closing a second switch also connected in series with the anode supply circuit of said apparatus.

10. A control circuit for thermionic rectifier apparatus, means for protecting said rectifier apparatus until a predetermined cathode temperature is attained, said means comprising an anode supply circuit, a slow acting thermostatic relay for closing a switch connected in series with the anode supply circuit, a quick acting electro-magnetic relay for closing a second switch also conneoted in series with the anode supply circuit of said apparatus.

11. A control circuit for a rectifier comprising a plurality of series switches for controlling the anode supply of said rectifier, at leastone of said A switches connected in series withan anode supply circuit and operated by a thermostatic relay and atleast one of the other switches also connected in series with said anode supply circuit and operated byan electro-magnetic relay.

12. A control circuit, for a thermionic device comprising a plurality of series switches for controlling the anode supply of said thermionic device, at least one of said switches connected in series with said anode supply and operatedby a slow acting thermostatic relay and at least one of the other switches also connected in series with said anode supply and operated by a quick acting electro-magnetic relay. V

DANIEL EDWARD ODONOVAN. 

